Conventionally, hair dye compositions in a form of liquid or cream have been broadly used, however it is not easy to apply them to hair evenly. When a consumer herself applies a dye to her own hair root or the back of her own head, not only skills in a hair blocking or two-mirror technique and the like are required, but also a careful manipulation is required for uniform application.
To simplify the dyeing procedure, it has been proposed to discharge the dye in the form of foam, and two-part aerosol dyes and one-part non-aerosol dyes have been known. Concerning the two-part aerosol dyes, there have been the following problems that: a mixture ratio of the first part and the second part is not constant and uneven bleaching or uneven dyeing is likely to take place; a high pressure metallic vessel may be corroded by oxidation by hydrogen peroxide; and the internal pressure of the high pressure vessel may rise excessively by decomposition of hydrogen peroxide. Concerning the one-part non-aerosol dyes, there have been the following problems that: due to non- or weak bleaching ability, it is difficult to change a color tone substantially with a single dyeing operation; and to dye to a brilliant color tone, it is required to leave the dye on the hair for a long period of time after application or repeat the operation thereby making the dyeing operation rather cumbersome.
On the other hand, two-part hair dye compositions to be discharged in the form of foam from a non-aerosol foamer vessel have been proposed (Patent Document 1 and Patent Document 2). By discharging a liquid mixture of the first and second parts from the non-aerosol foamer vessel in the form of foam, the mixture ratio thereof can be more constant than the conventional two-part aerosol dyes, and sufficient bleaching ability and dyeability compared with the conventional one-part non-aerosol dyes can be obtained.    Patent Document 1: JP-A-2004-339216    Patent Document 2: JP-A-2006-124279